1. Field of the Invention
This invention relates to aquatic life nutrients, and, more particularly, to the use as an aquatic nutrient of the phosphate compound LDPO.sub.4, wherein L represents a Lewis Acid moiety, and D represents a divalent metal moiety. It relates still more particularly to the use of this composition to support the food chain in water by supplying primary nutrients, secondary nutrients, and micronutrients to microbes, algae, fungi, and aquatic plants. These members, low in the food chain, are essential to the feeding of lower animal life forms, which, in turn, supply food for fish. Effective feeding of the lower members in the food chain is particularly important to the survival and growth of newly hatched and juvenile fish in flowing streams, estuaries, and lakes.
2. Description of the Prior Art
Although many streams contain excess nutrients and grow too much microbial material, algae and aquatic plants, many streams do not contain enough nutrients to support a food chain ranging from microbes and algae, to insect larvae, to fish, for example. These nutrient shortages usually occur in remote glacial streams and lakes in the cooler parts of the earth and are exascerbated by operations which remove the plant life from surrounding areas. For example, removal of timber can cause loss of the flow of nutrients from the area's soil, and, in turn, cause the nutrient concentrations in streams to decrease to a point where the survival rate of newly hatched and juvenile fish in the streams is severely decreased because of low food availability.
Slaney and Northcote in 1974 showed that food availability directly affects the abundance, growth rate, and the production of juvenile fish per unit of stream area. Increases in levels of inorganic nutrients in streams were shown by Johnston et al in 1990 to increase production of the lower members of the food chain thereby increasing insect abundance, which, in turn, increased the growth of fish.
The foregoing and other workers in the field have demonstrated the need and benefits of supplying nutrients to nutrient deprived streams to support fish, particularly in the early part of the fish life cycle. Ordinary fertilizers such as liquid or granular ammonium phosphates have been used with at least scientific, if not practical, success, by controlling addition rates to streams with drip or auger feeding systems. These soluble nutrients are dissolved, diluted, and soon carried away from the desired use areas by the water.
Ureaformaldehyde polymer nutrients have been tried but were found to release too quickly for effectiveness in water. Another problem with the ureaformaldehyde granules is their low density which allows the granules to be washed to undesired locations. This low density was also found to be a problem with polymer coated nutrient granules. Sulfur coated granules lost integrity and released their soluble nutrients too quickly.
This writer and others in the prior art have developed magnesium ammonium phosphate, and similar phosphate compounds, as controlled release terrestrial fertilizers. These fertilizers released their contained nutrients in and on the soil at about the same rate as ureaformaldehyde fertilizers and the granules behaved physically in a similar manner.
The prior art has not found a granular nutrient which may be used to substantially remain where it is applied in a flowing aquatic environment and supply nutrients in a controlled manner to the food chain providing food for fish.